Bride of the Barrier Master, Vol. 4 (manga)

Hana is approached by Sae, her old servant from the Ichise home, with a desperate plea to save Hazuki from the fate their parents have forced upon her. Ever since Hana left the family, her relationship with her twin has been frayed—and getting involved could mean sacrificing her new life of freedom. But when a crisis erupts at school, they might have no choice but to work together! Will Hana and Hazuki be able to rekindle their sisterly bond?